Microfluidic chips find use in many areas such as fluid mixing for chemical reactions, cell sorting, and electrophoresis, as examples, and often have both electrical terminals and microfluidic channels in which electrokinetic phenomena, which include electro-osmotic flow and electrophoresis, are generated.
Microfluidic chips suitable for capillary electrophoresis typically provide a carrier channel in which substances within a sample are separated by electrophoresis and detected, and a sample channel in fluid communication with the carrier channel for introducing samples into the carrier channel. Generally, samples and carrier fluids are manually introduced into the microchip by dropper, syringe, and the like, and these fluids flow through a network of channels by capillary action, external pressure or electro-osmotic flow. Voltages between a few hundred volts and greater than one thousand volts may be applied to the channels using electrical probes, for inducing electrophoretic and/or electro-osmotic flow useful for introducing small amounts of the sample fluid into the carrier channel at an intersection of the two channels. As stated, charged substances in the sample will separate in the carrier channel as a consequence of differences in electrophoretic mobility. At chosen locations, the fluid in the carrier channel may be optically or electrically interrogated yielding component analysis information for the sample.
Although certain substances within a sample fluid may be efficiently separated for analysis using conventional microfluidic chips for capillary electrophoresis, the handling, timing and delivery of very small fluid volumes to flow paths in the chip, along with the manual transfer of fluids to corresponding reservoirs, renders automated capillary electrophoresis for sample analysis difficult.